With the development of the technologies of wireless communication and information processing, portable electronic devices such as foldable mobile phones are now in widespread use. These electronic devices enable consumers to enjoy the convenience of high-tech services anytime and anywhere. Foldable electronic devices are particularly favored by consumers for their convenience.
Foldable electronic devices generally have two housings joined by a type of hinge that allows the housings to fold upon one another. Many such foldable electronic devices have most of the electronics in one housing, called the main housing, and a few electronics in the other housing, called the cover. Other such foldable electronic devices have all the electronics in the main housing, with the cover serving only to cover a keypad and a display of the main housing. Manufacturers are constantly seeking to reduce the volume, size and weight of these foldable electronic devices. Thus, it is desirable that the hinge coupling the main housing with the cover is modularized and miniaturized. A common modularized hinge device has moving parts such as a cam member, a cam follower and a spring held together in a unified structure. The structure is easily and quickly attached to the main housing and the cover during mass production. A miniaturized hinge device has as few parts as possible, with the parts being as small as practicable.
Referring first to FIG. 3, U.S. Pat. No. 6,321,415 B1 describes a hinge 10 used to connect a main housing and a cover of a foldable mobile phone. The hinge 10 comprises a shaft 12 having a washer fixed on a first end thereof, a spring 14, a cam 16, and a follower 18. The spring 14, the cam 16 and the follower 18 are all axially mounted around the shaft 12 one by one. One end of the spring 14 is fixed to the cam 16. A long, axial knob 161 is formed on an outside of the cam 16, for fixing of the cam 16 to the main housing. An opposite second end of the shaft 12 is surrounded by the follower 18. A mounting cavity (not shown) is defined in the mobile phone, for mounting of the hinge 10 therein. A first hole (not shown) is also defined in the mobile phone at a first end of the cavity, so that the first end of the shaft 12 protrudes out of the first hole. A second hole (not shown) is defined in the mobile phone at an opposite second end of the cavity, so that the follower 18 is fixed in the cover and protrudes out from the second hole.
When the main housing and the cover of the mobile phone are in an open state, the spring 14 has an original length, and an end surface of the cam 16 and an end surface of the follower 18 cooperate with each other compactly. When the cover is rotated toward a closed state of the mobile phone, the follower 18 makes the cam 16 rotate. The spring 14 is twisted and acquires elastic potential energy, and finally the cover is locked at the closed state by a flip-latch. When the cover is unlocked, it automatically rotates back to the open state by reason of the spring 14 releasing its potential energy.
However, the cam 16 cannot engage steadily with the follower 18. In addition, when the cover is opened, the spring 14 is liable to drive the cover to impact the main housing. The impact may damage the cover, the main housing, or the hinge 10. Furthermore, the hinge 10 is complex and difficult to assemble.
What is needed, therefore, is a simple, stable hinge mechanism which can be operated steadily and safely.